Recently, as semiconductor etching technology is enhanced, it is possible to perform various kinds of processing on various semiconductors or metals. In the etching technology, dry etching by plasma using a reactive gas (plasma etching) and wet etching using a chemical liquid are mostly used, and the etching is separately used depending on the use.
For example, when a silicon carbide (SiC) substrate containing SiC, which is an etching target, is etched, plasma etching is used, in which a metal mask such as aluminum is used as a mask. Here, the metal mask is produced by forming a metal film on the SiC substrate and patterning an etching pattern with an opening on the metal film.
Wet etching may be used for forming the etching pattern of the metal mask (see, for example, Patent Document 1). This is because reducing the thickness of a resist film is much easier than etching a metal film due to the relationship of etching selection ratio between the metal film and the resist, and thus, it is difficult to etch a metal film with a sufficient thickness in plasma etching.
As described above, when an etching pattern of a metal mask is formed by wet etching, a resist with the same pattern as the etching pattern is formed on the metal film, the resist is put in a dissolution-removable chemical liquid (etchant), and the exposed portion is wet etched.